Sooth ski: measured data from 3000+ skis!

A

alude

Member
Hi guys,

I am new here. I have been measuring skis for 15+ years, first as an undergrad design project, then in a research lab and now through a startup (Sooth Skis). We measure the "fundamental properties" of skis along their full length (e.g., width, height, mass, bending stiffness / flex and torsional stiffness), so you can know, for example, that the tip of a ski is much stiffer than another ski. We think this is better than just having an average number. We also measure the torsional stiffness, which is a big part of what make a ski being playful or grippy. We found that freeskiing skis generally have a low torsional stiffness for more playfulness...

Anyways, after measuring that raw data, we convert it into slightly more useable numbers and graphs. We still have work to do on that front and hope that the community can provide feedback. All the data is available online in a "comparator". Access is free. No registration needed. You can access the comparator here:

https://compareskis.shinyapps.io/compare/

We have more than 3000 skis in the comparator now, including 1200 from 2021-22. We try to measure all the lengths available, as each company scale their skis differently.

We think this can help people shop for skis. We also think that over time each skier will get to know what they personally like in a ski and be able to use the comparator efficiently. It is still very raw information, but once you start using it we feel there is no going back. We don't really know where this will lead us, but we would like to continue measuring skis if other people also find it useful. We think this can be complementary to on-snow reviews, and specially useful when reviews are not available in the model/length of interest or if you can't demo.

We are still missing many brands, but are very willing to measure any skis manufacturers would send us. So far we have been measuring skis from what is available in shops around Quebec, including Ski Michel, Oberson, Ski Town, D-Structure, Sport Radical and Ski Essentials. We are thankful for their help. Please encourage them if you can.

I will reply to a few recent threads with exemples on how to use the comparator. We think it is pretty self explanatory, but we wrote a short tutorial the basic functions:

https://soothski.com/compare-skis-with-measures/2021/ski-comparison-application-guide/

Hope you find this useful!

Alexis
 
14354129:mystery3 said:
Can you do boots next? You could singlehandedly standardize the flex rating system and create an actual flex index.
Click to expand...

Ahaha! Yes, we thought [are thinking] about it. We know that it is a huge pain for everyone.

It is much harder to do it right with boots. Plastic properties depend on temperature and testing speed. Overall flex also depends somewhat on fit. If people like this kind of stuff for skis, we might continue with boots! :-)
 
Dude this is some of the absolute dopest shit I’ve ever seen!! Big ups to you! This is definitely getting saved on my favorites to be used often when talking to people about different skis! Thanks a million for this!!
 
Alexis at first glance this is amazingly robust and super useful for ski shop and gear nerds. Can’t wait to dive deep into the data. Thanks for sharing
 
14354208:JohnJonsz said:
Alexis at first glance this is amazingly robust and super useful for ski shop and gear nerds. Can’t wait to dive deep into the data. Thanks for sharing
Click to expand...

Thanks!

Regarding robustness, we try our best to minimize any error. Most of the process is somewhat automated to minimize operator error. But please report anything you find weird with the data so that we can review and correct it if needed.
 
14354224:gucciskrr said:
Wtf so most waist width values are skinnier than advertised?
Click to expand...

We measure the width at every mm along the full length of the ski to the nearest 0.1 mm with our machine. We then find the narrowest point and display that value rounded to the nearest mm in the comparator as the waist width. You could get slightly different results depending on how you measure.

If you measure the width with caliper, you would likely get slightly larger results than us as you have very little chance of finding the point of minimum width as accurately as we do, while also staying perfectly perpendicular to the longitudinal axis to get the true width. I looked quickly at the 15 first reviews on Blister, and all their tip-waist-tail measured dimensions (using caliper) are also smaller than what is advertised. You can find difference as big as 2-3 mm.

It is unclear to me how the marketing departments are taking their measurements... but for sure, it is not always with a ruler! At the same time, we don't think you should get bogged down for 1-2 mm differences.

If you have anything specific that seems weird, we will be happy to review our log files and calibration.
 
14354149:alude said:
Ahaha! Yes, we thought [are thinking] about it. We know that it is a huge pain for everyone.

It is much harder to do it right with boots. Plastic properties depend on temperature and testing speed. Overall flex also depends somewhat on fit. If people like this kind of stuff for skis, we might continue with boots! :-)
Click to expand...

Boots would be super cool. One thing I'd love to see data on is the linearity/progressiveness of forward flex. In my experience, 3-piece boots (like Full Tilt) are more linear flexing than 2-piece boots which ramp up in stiffness quite quickly, however without good data its really just a hunch.

Additionally for skis information on damping and natural frequencies would be super cool. I'd imagine that would be a huge increase in scope but if you went for it fortunately there is an ISO standard for ski damping (ISO 6267). I don't think that ISO standard includes torsional bending modes though, which is a shame because Fosse and Glenne (2007) suggest that torsional vibrations are quite important.
 
This is such fuckin cool tool you guys made. Thanks for sharing with Newschoolers. aight imma go nerd out about this for an hour
 
Good ol ggplot. I need to learn shiny.

Anything surprising in here? Things that are highly correlated that you didn't expect and such?
 
Torsional stiffness of the 16/17 mantra's is crazy. I knew they were legendary skis, it's cool to see some stats that back it up.
 
such a great idea! i hope this gets taken somewhere because i can only imagine how many ppl it would help. basically doin gods work at this point
 
Wtf, this was something I daydreamed about if I won the lottery one day, only you're doing way better than I imagined. I'm going to be lost in these numbers for a while!
 
OP, are you a professional data analyst? Seems like a passion that was discouvered in high school, then find a gig in the same field. Thats all around very impressive notherless.

keep up the good work!
 
Super cool! Next would be to test how the skis stand up to abuse. It would be cool to test force or momentum that it takes to break each skis edge with a steel tube.
 
Imagine the effect this could have on things like Blister reviews - where subjective "hand flexing" the skis and then ascribing a number like 7.5 is used. This would standardize flex across the board in reviews.
 
14354685:treyroeseler said:
Super cool! Next would be to test how the skis stand up to abuse. It would be cool to test force or momentum that it takes to break each skis edge with a steel tube.
Click to expand...

I'm assuming the shops they are working with wouldn't be too stoked on that.
 
On my phone and didnt drive too into it. But I remember a roofbox review of some Vishnu skis and overtime they ended up losing camber/rocker and becoming quite flat. Does this machine do an initial test right out of the box or was it done multiple times?
 
This is so sick!!!

just got to learn some cool stuff. Like I had no idea that the Head Oblivion was extremely comparable to the edollo! Who woulda thought. Not me!
 
14354366:IsaacNW82 said:
Boots would be super cool. One thing I'd love to see data on is the linearity/progressiveness of forward flex. In my experience, 3-piece boots (like Full Tilt) are more linear flexing than 2-piece boots which ramp up in stiffness quite quickly, however without good data its really just a hunch.

Additionally for skis information on damping and natural frequencies would be super cool. I'd imagine that would be a huge increase in scope but if you went for it fortunately there is an ISO standard for ski damping (ISO 6267). I don't think that ISO standard includes torsional bending modes though, which is a shame because Fosse and Glenne (2007) suggest that torsional vibrations are quite important.
Click to expand...

Well, if you know Foss and Glenne, we can nerd out a bit! :-)

Vibration

I am still not sure exactly what we should measure to make it useful to skiers. There is very little damping in skis and how a ski vibrates depends mostly on its shape, stiffness and mass. Take a look at our very recent work: https://rdcu.be/cAYY7. Torsional and even hybrid modes are super important.

We could calculate a few things from our current measurements that are related to vibration (mode, frequency), but if you look at stiffness and weight/surface-to-weight ratio, you will start seeing things! ;-)

The surface-to-weight ratio tells you how much heavy stuff the designer put in a ski. It is better than just the mass to tell you what kind of construction was used because a ski naturally gets heavier with length and width. Heavy/dense material are titanal, rubber, plastics, dense woodcore, ... Denser materials generally have more damping (in an engineering sense), but mass in itself also correlate very clearly with the "perception of damping" while skiing.

Anyways, suggestions are welcome. Some people even asked us to measure the sound that it makes when you tap on the ski tip... Some people shop for skis that way! We are listening.

Inertia

I think more importantly to people on this forum would be the position of center of mass around the mount point and the inertia of the ski in a few directions. This would relate to how easy it is to maneuver a ski up in the air. Anyone would find that interesting? It is not that hard to do...

Boot

Lot of great work out there on the measurement of torque vs angle at different flexing speed. However, it is hard to measure a "fundamental" number that nobody will debate. With skis, we measure fundamentals quantities. No matter how you measure skis and what machine you use, if you are looking for EI (bending stiffness) and GJ (torsional stiffness), you would get the exact same result as ours.
 
14354380:DrZoidberg said:
Good ol ggplot. I need to learn shiny.

Anything surprising in here? Things that are highly correlated that you didn't expect and such?
Click to expand...

Lots of things to talk about! We will try to cover some of that in a few articles... But if you find anything, please post it here so that we can discuss it!

What is cool is that you can see where some of the "feel" of some brands is coming from. As someone pointed out, Volkl skis are typically fairly stiff in torsion. This is kind of the DNA of their brand and can explains a lot of their feel. You can also see, for exemple, that both the ZeroG and Tour 1 constructions are similarly super light when looking at the surface-to-weight ratio, but that one construction keeps more bending stiffness (ZeroG) while the other keeps more torsional stiffness (Tour 1). When you make things light you can keep everything, you have to make a choice.
 
14354391:a_pla5tic_bag said:
You should look at distributions of stats over time, like waist width, etc. It'd be funny to see how it changes over time.
Click to expand...

We did a little bit of this with the Vermont Ski Museum. Enjoy the read:
https://www.mdpi.com/2504-3900/49/1/135

We didn't find anything that great, partly because the Vermont Ski Museum mostly just keep skis pre-70s. They don't find skis from the 1990-2021 era very historically interesting, so we are missing most of the recent innovations with regard to ski shaping...

I think that in 2-3 years we will be able to create these trends with the most recents skis in our database. The data from the last few years is highly skewed toward what we could measure near us on the East Coast. Now with 1000+ skis annually, we should have nice stats! :-)
 
14354685:treyroeseler said:
Super cool! Next would be to test how the skis stand up to abuse. It would be cool to test force or momentum that it takes to break each skis edge with a steel tube.
Click to expand...

That would be nice. The challenge is that is you break a ski you have to pay for it! We don't have these funds. Also, in an ideal world, destructive testing is done on a few samples before you do any comparisons, which makes everything even more expensive.

So far we go to shops and use our machine to measure their skis. You can take a look here to see our patented process, but basically we take a ski from the rack, unwrap it, measure it and put in back in the rack unharmed. The nice thing is that it takes us less than 2min to measure everything on a single ski. This is what allows us to measure so many skis and could potentially make this viable long term. Most techniques that we know of are not as accurate and take much much longer.

For the record, shops are just kindly opening their doors to us. We measure and put the numbers out. No filter of any kind. Initially nobody understood what we were doing and they were awesome to just let us do our thing. Now, they are starting to appreciate that they can use this data to help each customer choose the best product for them. They would love to have data on durability. Having an unhappy customer return with a broken ski is bad business for everyone involved...
 
14355365:THE-Albino* said:
This is so sick!!!

just got to learn some cool stuff. Like I had no idea that the Head Oblivion was extremely comparable to the edollo! Who woulda thought. Not me!
Click to expand...

Yep, very close. Slight difference in tail rocker. Also, if you look at the stiffness distributions, you will see that the Oblivion's tail is softer. The mass of these two skis is also very different (300g).

Note that the Oblivion 84 and 94 are quite different. The 84 is not very similar to the Edollo.
 
14355407:alude said:
Yep, very close. Slight difference in tail rocker. Also, if you look at the stiffness distributions, you will see that the Oblivion's tail is softer. The mass of these two skis is also very different (300g).

Note that the Oblivion 84 and 94 are quite different. The 84 is not very similar to the Edollo.
Click to expand...

Absolutely. And I was using the 94 for the comparison just forgot to mention. It just seemed so weird to me that head wouldn’t make a stiff super cambered park ski. Even weirder there’s very little mention of the softness on their website. This just makes this sooth ski site that much better. It tells us what companies are exaggerating and or not telling us.
 
14355366:alude said:
Well, if you know Foss and Glenne, we can nerd out a bit! :-)

Vibration

I am still not sure exactly what we should measure to make it useful to skiers. There is very little damping in skis and how a ski vibrates depends mostly on its shape, stiffness and mass. Take a look at our very recent work: https://rdcu.be/cAYY7. Torsional and even hybrid modes are super important.

We could calculate a few things from our current measurements that are related to vibration (mode, frequency), but if you look at stiffness and weight/surface-to-weight ratio, you will start seeing things! ;-)

The surface-to-weight ratio tells you how much heavy stuff the designer put in a ski. It is better than just the mass to tell you what kind of construction was used because a ski naturally gets heavier with length and width. Heavy/dense material are titanal, rubber, plastics, dense woodcore, ... Denser materials generally have more damping (in an engineering sense), but mass in itself also correlate very clearly with the "perception of damping" while skiing.

Anyways, suggestions are welcome. Some people even asked us to measure the sound that it makes when you tap on the ski tip... Some people shop for skis that way! We are listening.

Inertia

I think more importantly to people on this forum would be the position of center of mass around the mount point and the inertia of the ski in a few directions. This would relate to how easy it is to maneuver a ski up in the air. Anyone would find that interesting? It is not that hard to do...

Boot

Lot of great work out there on the measurement of torque vs angle at different flexing speed. However, it is hard to measure a "fundamental" number that nobody will debate. With skis, we measure fundamentals quantities. No matter how you measure skis and what machine you use, if you are looking for EI (bending stiffness) and GJ (torsional stiffness), you would get the exact same result as ours.
Click to expand...

If you're talking about inertia of a spinning ski, I think it would be super interesting to see the centroid of a ski compared to the center of mass. Wonder if it would correlate with flex pattern. ie a ski with a center of mass in front of the centroid would be stiffer in the nose than the tail
 
14355366:alude said:
Well, if you know Foss and Glenne, we can nerd out a bit! :-)

Vibration

I am still not sure exactly what we should measure to make it useful to skiers. There is very little damping in skis and how a ski vibrates depends mostly on its shape, stiffness and mass. Take a look at our very recent work: https://rdcu.be/cAYY7. Torsional and even hybrid modes are super important.

We could calculate a few things from our current measurements that are related to vibration (mode, frequency), but if you look at stiffness and weight/surface-to-weight ratio, you will start seeing things! ;-)

The surface-to-weight ratio tells you how much heavy stuff the designer put in a ski. It is better than just the mass to tell you what kind of construction was used because a ski naturally gets heavier with length and width. Heavy/dense material are titanal, rubber, plastics, dense woodcore, ... Denser materials generally have more damping (in an engineering sense), but mass in itself also correlate very clearly with the "perception of damping" while skiing.

Anyways, suggestions are welcome. Some people even asked us to measure the sound that it makes when you tap on the ski tip... Some people shop for skis that way! We are listening.

Inertia

I think more importantly to people on this forum would be the position of center of mass around the mount point and the inertia of the ski in a few directions. This would relate to how easy it is to maneuver a ski up in the air. Anyone would find that interesting? It is not that hard to do...

Boot

Lot of great work out there on the measurement of torque vs angle at different flexing speed. However, it is hard to measure a "fundamental" number that nobody will debate. With skis, we measure fundamentals quantities. No matter how you measure skis and what machine you use, if you are looking for EI (bending stiffness) and GJ (torsional stiffness), you would get the exact same result as ours.
Click to expand...

Oooooooo very nice paper! I agree a useful value for vibrations is a tricky one as there is a lot going on, so I'm not sure either. Personally, as a nerd, estimated natural frequencies for the first longitudinal and torsional mode shapes, plus some damping coefficient would be super interesting to have good data on. I for one am interested in how well harmonics of the bending mode resonate with the torsional mode and If there are any noticeable trends with that and the way skis feel on snow (perhaps the peaks of the frequency response diagram would be more pronounced?).

Now, Is it particularly useful information, especially to someone without a strong engineering/physics background who would likely be either misled or confused trying to interpret it? Eh, quite possibly no, especially after reading Gosselin, Truong, and Desbiens' (2020) paper about ski damping technologies and how all but one didn't really do much despite the marketing. Additionally, I think the influence of excessive camber and poorly thought out rocker can be important as well.

As far as interia goes, the "swing weight" if you will is a very useful stat to freeski/park and even many freeride skiers. The only really important axis I see there would be rotation around the vertical axis (i.e. a spin). I don't think inertia about the "backflip" axis, if you will, is that important as 1. It seems to correlate pretty well with mass (as you rotate very far from the neutral axis of the ski) and 2. It never seemed to impact my backflips/frontflips all that much, doing them on 178 park skis felt pretty similar to my 196 powder skis. So yes, "swing weight" would be great. Most of the people who car about these types of things also ride center mounted skis too, so simply about the neutral axis or center of the ski should be fine.
 
This is cool but i would really like to see a simple stress/strain curve for all the bindings. You could do it just like materials testing for failure.

also base friction would be an awesome test to get data for.
 
14355366:alude said:
Inertia

I think more importantly to people on this forum would be the position of center of mass around the mount point and the inertia of the ski in a few directions. This would relate to how easy it is to maneuver a ski up in the air. Anyone would find that interesting? It is not that hard to do...
Click to expand...

This would be a dream come true, not knowing this had made ski decisions much harder.
 
14355543:mrk127 said:
If you're talking about inertia of a spinning ski, I think it would be super interesting to see the centroid of a ski compared to the center of mass. Wonder if it would correlate with flex pattern. ie a ski with a center of mass in front of the centroid would be stiffer in the nose than the tail
Click to expand...

Yes it is correlated. One of the reason is that many manufacturers adjust the flex by changing the thickness of the core, which also changes the mass distribution. We are not showing our estimate because it would not give credit to the manufacturers who are doing more complex things with their laminate to reduce the inertia of their ski (e.g., lighter material at the tip/tail). However, I am not sure who is doing that and to what extend. We would need to measure some skis to answer that question...
 
14356073:IsaacNW82 said:
Oooooooo very nice paper! I agree a useful value for vibrations is a tricky one as there is a lot going on, so I'm not sure either. Personally, as a nerd, estimated natural frequencies for the first longitudinal and torsional mode shapes, plus some damping coefficient would be super interesting to have good data on. I for one am interested in how well harmonics of the bending mode resonate with the torsional mode and If there are any noticeable trends with that and the way skis feel on snow (perhaps the peaks of the frequency response diagram would be more pronounced?).

Now, Is it particularly useful information, especially to someone without a strong engineering/physics background who would likely be either misled or confused trying to interpret it? Eh, quite possibly no, especially after reading Gosselin, Truong, and Desbiens' (2020) paper about ski damping technologies and how all but one didn't really do much despite the marketing. Additionally, I think the influence of excessive camber and poorly thought out rocker can be important as well.

As far as interia goes, the "swing weight" if you will is a very useful stat to freeski/park and even many freeride skiers. The only really important axis I see there would be rotation around the vertical axis (i.e. a spin). I don't think inertia about the "backflip" axis, if you will, is that important as 1. It seems to correlate pretty well with mass (as you rotate very far from the neutral axis of the ski) and 2. It never seemed to impact my backflips/frontflips all that much, doing them on 178 park skis felt pretty similar to my 196 powder skis. So yes, "swing weight" would be great. Most of the people who car about these types of things also ride center mounted skis too, so simply about the neutral axis or center of the ski should be fine.
Click to expand...

I honestly think that vibrations is a very small part of the on snow feels, except maybe in a very few conditions (e.g., super hard snow, super high speed, just after takeoff from a jump). I could be wrong though...

Very interesting observation about the ski's contribution to the swing weight of spin vs backflip. It also makes total sense. When you spin, the ski tip/tail are the furthest away from your axis of rotation and are probably the main contributor to inertia. When you backflip, you have your feet/boots as far away as the skis, and you would have more trouble feeling the ski. Happy to measure one less axis! :-)

I think it would be nice to have an "inertia comparator" that takes into account the inertia of the ski and the mount point position w.r.t the center of mass. That seems to come up often in the reviews.
 
14356739:dolanslebensraum said:
This is cool but i would really like to see a simple stress/strain curve for all the bindings. You could do it just like materials testing for failure.

also base friction would be an awesome test to get data for.
Click to expand...

For binding, you mean get the elasticity of the binding?

You are interested in forces/moments in all directions or just a few?

What would you look for in these curves?
 
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